As the oil and gas industry moves offshore into deeper waters, more gas will also be discovered. Offshore production of LPG is the natural extension of offshore oil production. Some of the gas will be associated with gas produced with oil and other discoveries will be gas reservoirs. Demand for LPG is rising, particularly in the residential and commercial sectors. The use of cleaner liquid and gaseous fuels is expected to continue to increase as populations grow and total demand for energy rises proportionally. As oil and gas prices rise, the economics of liquefied gas improves and results in more demand for LPG.
LPG is a mixture of ethane, propane, and butane and may contain minor quantities of other light condensable hydrocarbons associated with production of oil and gas. At ambient temperature and pressure, LPG exists as a gas, but it can be cooled and/or pressurized to provide a liquid, which facilitates storage and transportation. LPC can be liquefied at pressures between 100 psig and 150 psig at ambient temperatures.
The current state of the art proposes to extract LPG from natural gas and store it on intermediate FPSO units or in elaborate and expensive tanks built in the processing facility prior to offloading it to export carriers. In addition, LPG has been produced at offshore terminals and transported to LPG storage/processing facilities onshore by means of a subsea pipeline to the onshore facility. As such, these facilities need to be deployed close to the shoreline.
Offshore collection, transfer, and transportation of LPG present many challenges. There are many aspects of offshore LPG production that are in need of improvement to make the process commercially viable.